Improved furnace for boasting ores



D. J. OHARRA & O. B. THOMPSON. FURNACE FOR ROASTING 0113s.

Patented Aug. 6, 1867.

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DAVID JON ES OHARRA AND CLARK BROWN THOMPSON, OF EMPIRE CITY, NEVADA.

Letters Patent No. 67,445, dated August 6, 1861'.

IMPROVED FURNACE FOR ROASTING ORES.

TO ALL WHOM IT MAY CONCERN;

Be it known that w DAVID J. OHnnnn and CLARKB. THOMPSON, of Empire City, Ormsby county, State of Nevada, have invented certain new and useful Improvements in Furnaces for Desulphurizing and Chloridizing Ores; and we do hereby declare the following description and accompanying drawings are suficient to enable any person skilled in the art or science to which it most n'oarlyappcrtains to make and vuse our said invention without further invention or experiment.

The nature of our invention rclates to the employment of a longitudinal furnace, more especially adapted to the roasting of ores, havinga fiat sole and roof'in order to confine the, heat to the bottom and surface of the ore, and heat it up gradually, the fire being placed at intervals along the said furnace, and the ore stirred at intervals by'hoes attached to an endless chain passing through it. The furnace being open at both ends the hoes-receive the ore at one end and discharge it at thcother roasted. Referring to the drawings-- Figure 1 represents a side elevation of our furnace,

Figure 2, a plan.

Figure 3, an end view.

Figures 4 and 5, plan of-hces or conveyors.

We construct our furnace of the usual materials and of different dimensions. We think about eighty feet long and forty-one feet wide the most suitable size The hearth A is a perfect plane as well 'as the fiat roof B. At each end of the furnace we attach a'grooved pulley, C and C. Around these pulleyspasscs'an endless chain, .1), passing completely through the furnace. Conveyors E and E are'attachcd to this chain at equal distances, and are constructed in the form of a circular iron frame divided into two semicircles along a line perpendicular toits line 0f motion, and hinged with book and eye to allow it to double together in passing over thepnlleys C G. On the-bottom of these conveyors we.

place four hoes oh a a at an angle of about forty-five degrees with the axis of the furnace, while the centre hoe is composed of two hoes inclined towards each other, and firmly attached together along their forward vertical edge, forming an instrument resembling a double mould-board plough. This hoe ploughs-throngh the ore along the centre of the hearth, throwing it in either direction and leaving a furrow behind it. The hoes on the opposite edge of the circular plate, however, following the leading hoe, andhaving their faces inclined in the opposite direction, throw the ore back and fill up the furrow again. All the hoes attached to the circular plate are arranged and inclined, as shown in the drawings, with special reference to, producing this efi'ect upon the ores, alternately ploughing them in one direction and then in the other, so as to produce a thorough agitation of the contents of the ore-chamber. The circular plates or conveyors are niadc'of suflicient size to extend across the entire width of the hearth, and are attached in a suitable manner to the endless chain D and carried with it through the ore-chamber, from the entrance to the outlet, returning over the top of the furnace, as shown in the drawings. 'In passing back over the furnace thechain D and circular plates hecomesuiiiciently cooled; the distance travelled by them in the open'air being about one hundred feet. With our furnace we do not need to pass the chain through a cooling cistern of'water, but, on the contrary, we avoid it, for the reason that the conveyors and hoes, if they entered the furnace wet, would communicate their dampness to the ore, coking it and sticking it to the chain, plate, and bees so as to interfere with theiropcratio'n, and accelerate altogether too greatly the forward movement of the ore in the chamber. The furnace is provided with one, twofor three fire-chambers G G, according to the length occupied by thchearth. The first is placed about twenty-five feet from where the ore is fed, and throws the heat about twenty feet, coming in contact with the ore while it is being conveyed from a comparatively cool place and heated up evenly and gradually-to 800 Fahrenheit, which heat is increased a little in passing the last fire-chamber:

The operation of our furnace is .as follows: The ore is fed in a pulverized state through the hopper H, placed in front of the flue I, and the conveyors are driven slowly by the pulleysfl As the conveyors E E,

carried along by the chain D, pass slowly through the ore-chamber, the bees at: a a, projecting down into the ore, plpugh through its mass, as above described, moving it forward a little every time they pass through it, and thus gradually advancing the whole mass ofore towards the discharge end of the chamber, at the front of the is so greatthat it becomes necessary to are furnace. As it passes along it is alternately heated and cooled by its position in front of the several fires or in the comparatively cool space between them. This alternate heating and cooling repeated several times is indispensable to the perfect reduction of the ores; for it is not one base metal alone from which we have to-free the silver or gold, but many, each of them requiring a difl'erent'treatm'ent toexpel them from theore, or detach them from the valuable metal which is sought. Once heating and cooling will separate some of the base metals, others will not separate tillthe 'orehasbeen heated to a ccrtain-degree-cooled and heated again to a higher degree than before. It is to so alternately heat and cool the mass of ore as to bring to bear upon it successively, during its passage through the furnace, all the-conditions required to expel all the base metals usuallycombincd with it, that we have invented our furnace. And we may remark here that in order to perfect the treatment of the ore the several fires should-be of different degrees of intensity, preferably increasing their heat as we approach the delivery end of the ore-chamber The timeoccupied by these conveyers in passing through the furnace must depend somewhat upon the quality of the ore to be roasted; for a poor or second-class ore the conveycrs may be driven rapidly through, every six or eight minutes, whilethe ore is kept stirred at the rate of fifteen or sixteen feet per -hour, which gives it about five heurs roasting in an eighty-foot furnace. For ore that requires longer roasting the speed is lessened, and the ore is consequently longer in passing through the furnace. For a; longer or shorterfurnace the speed is rcg ulated accordingly.

The present-way'of roasting ores is very imperfect, as well as expensive. The first objection to the Freiberg furnace, and, in fact, all others how in use, is that a portion of the ore lyingnear the fire-chamber receives too sudden and heavy a heat atfirst, thereby preventing certain beneficial chemical changes from taking place; and,

furthermore, where salt or chlorine isemployed, the salt will dec'omposeand the chlorine volatilize before the silver is liberated from the sulphur, and thus leaving the metals to enidize which will not admit of free amalgamation. The second objection which may be urgcd in this connection is the stirring in the common furnace. The lighter p 'articles of ore' and chlorides willrise and be carried oil by the draught; and, thirdly, their arches not being flat enough to confine the heat to the surface and bottom of the ore, the superficial area of the hearth h the roof in order to secure it, leaving a large space between the roof and surface of the ore; the consequence is much more fuel is required.

By this construction and use of our furnace, we claim to have overcome these imperfections and deficie'n-l cies. We heat up gradually and uniformly, the stirring being performed so gently as to lose nothing by'draught, confining the heat to thesurface and bottom of the ore, and consuming the. smoke, our machinery being so perfect that one-horsepower and one man will roast the same amount of ore that inother furnaces will require a large power and six men to accomplish the same,

Having thus described our invention, what we claim as new, and dcsire to secure by Letters Patent, is- 1. The combination and arrangement of the hingcd circular plate E E vwith the inclined oblique hoes a a a a, all constructed as shown, and attached to the endless chain D, substantially as and for the purpose specified.

2. The arrangement of a series of lire-chambers G G along the sides of the orechamber of a dcsulphuriz,

ing furnace, at intervals'of about twenty-five feet, substantially in the manner and for the purpose-sot forth.

DAVID J. OHARRA, [as] c. n. THOMPSON. 1.8.3

Witnesses:

A. J. Lo'cxwoon, Janus Mom'us. 

